2:24 p.m.: At the scene, we heard there were 12 witnesses to the event. As of now, nobody has stepped forward, Sheriff Ken Mascara said as he ended the news conference.

2:21 p.m.: Two crime scenes exist, Mascara said. The first is where the traffic stop occurred and the second is where Semer was shot.

2:19 p.m.: Mascara said Semer fled in his car, running over one officer and with another officer partially in the car. When he stopped, Semer fled on foot.

2:17 p.m.: "Rumors and gossip do not help in getting the truth," Mascara said. Both officers involved in the shooting have been with the department for years. At least three shots were fired and both officers fired their weapons. Mascara would not say whether Semer had a weapon.

2:14 p.m.: An autopsy will be today or tomorrow, Mascara said. "We need our community's help on this case," Mascara said, adding that no witnesses have come forward.

2:12 p.m.: Sequence of events Saturday night were: Demarcus Semer was traveling north on North 19th Street when a Fort Pierce police officer tried to stop him. Why he tried to stop Semer is not yet known. When Semer did not stop, the officer radioed for backup.

Semer ran over an officer and the backup officer was trapped inside the vehicle, Mascara said.

2:03 p.m.: The St. Lucie County Sheriff's Office is asking for the community's help in the investigation, said Sheriff Ken Mascara. Investigation will be comprehensive, objective and thorough.

1:55 p.m.: The start of the news conference, originally scheduled for 2 p.m., has been postponed 10 minutes.

Here's what we've reported in the shooting case so far today, before the news conference:

Editor's Note: The location of the shooting has been changed, with updated information.

FORT PIERCE — Both officers involved in the fatal shooting of a fleeing motorist have been put on administrative leave as the St. Lucie County Sheriff's Office conducts its investigation into the incident, police Deputy Chief Frank Amandro said Monday.

The move is standard in such cases, he said.

According to the Sheriff's Office, during a traffic stop about 11:55 p.m. Saturday night, motorist Demarcus Semer, 21, of Fort Pierce, ran over one of the officers, injuring his leg, as a second officer was getting in Semer's vehicle.

The second officer couldn't get out of the moving ca, which stopped about 600 feet farther in a residential area on North 19th Street near Avenue G, according to a sheriff's news release.

Semer was shot outside the car. He was pronounced dead at the scene. The injured officer was treated at Lawnwood Regional Medical Center & Heart Institute and released.

"During the traffic stop, the driver attempted to flee," said Sheriff Ken Mascara in a prepared statement. The sheriff scheduled a news conference at 2 p.m. Monday to discuss the incident.

After the incident, Police Chief Diane Hobley-Burney asked the Sheriff's Office to investigate the shooting to ensure impartiality.

She is "asking our community to be patient and calm while these investigations are conducted," she wrote in a prepared statement. "It is important that the community is aware that each time a life is lost, it is a tragedy for all, regardless of the circumstances."

She promised that the Police Department will be transparent during the inquiry.

Once complete, the Sheriff's Office investigation will be turned over to the State Attorney's Office for review. Then a grand jury will be convened to see whether indictments should be issued.

Semer's grandfather, Elijah Smith, of Fort Pierce, said Semer had been with a group of friends practicing rap music before the shooting. The house where they met is on North 19th Street, where the shooting occurred.

Smith said Semer had just completed his first week of work at Medical Data Systems in Vero Beach. Prior to that, he worked as a bank teller at Walmart in Fort Pierce. "He was a nice good young man," Smith said.

Semer was a quarterback and wide receiver at Fort Pierce Central High School in 2012-2013. He attended college in Chicago for about a year, then returned to Fort Pierce, Smith said.

Fort Pierce Central's former football coach, Josh Shaffer, said Semer was a vital part of the team. "This is a shock. It is tragic. He was a brilliant young man who was so personable," Shaffer said.

"He was a natural leader who could make a connection with about anyone, Shaffer said. "He cares about everyone."

According to the Sheriff's Office, Semer did not have a criminal record in St. Lucie County.

Anyone with information about the shooting incident is asked to call the St. Lucie County Sheriff's Office at 772 462 3230.